The present invention relates to the use of solar heat energy to generate electricity. The invention defines a method, which produces electricity using a photochromic medium, which captures and contains solar energy at moderate temperatures. The heat energy contained in the medium is converted to electric energy in a generating system, which increases the kinetic force of the medium flow sufficient to drive an impeller, which drives the stator of an electric generator.
We have been unable to locate any prior art which pertains to the use of a photochromic heat exchange medium as a means to effect an energy conversion of heat induced fluid flow to drive a generator of electrical energy.
There is, however, a substantial body of prior art, which relates to the use of temperature differences in various depths of seawater to generate electricity, generally termed Ocean Thermal Energy Conversion (OTEC). Flynn, et al., U.S. Pat. No. 5,513,494, teaches the use of the temperature differences inherent in different depths of seawater and by vaporizing the warmer water generates electricity in a vapor driven turbine. Flynn does not teach the use of a photochromic heat exchange medium to store energy or convert that energy to electricity.
Ocean Thermal Energy Conversion methods have demonstrated marginal economic results due primarily to the limited heat retention capacity of water and the substantial energy and cost required to pump colder ocean water occurring several thousand feet below the surface to the vessels at the surface in which the systems have been contained. These systems are limited to ocean sites where depths are sufficient to offer the temperature differences required.
The photochromic medium utilized in the invention provides a heat containment capacity from 4.5 to 8 times greater than that of water which, in part, assures a substantially more efficient method.
Mochizuki, in a paper presents a means different than that cited in Flynn and by others for directly exposing the ocean water collected at different depths thereby converting those temperature differences to mechanical energy.
Photovoltaic systems for the generation of electrical energy directly from solar light sources are in broad use particularly in areas where electric utility power is not available. These systems utilize a silicon base structure, which accepts a portion of the solar spectrum directly stimulating small packets of photon energy, which are transformed to electrons. Due to the limited means for generation of photons, a substantial surface of silicon must be exposed to generate effective power. Due to the conversion of solar light to directly generate electric power this method is not comparable to the present invention. The economic result is a cost of electric power, which is three to four times greater than the average cost of power provided by utilities in most areas. This may be compared with a projected cost of electric power generated by the invention 75% lower than that presently provided by most utilities. The advantage of the invention over photovoltaic systems is significant.
The stirling engine expands a confined gas through exposure to concentrated heat. Versions of the engine concentrate solar heat to expand the gas. The expanded gas produces mechanical power in a cylinder enclosing a piston. The expanded hot gas is then cooled and returned to the chamber and the cycle begins again. The engine is able to transform heat into effective work because the expansion of the gas at high temperature delivers more work than is required to compress the same amount of gas at low temperature. The necessity of rapid removal of heat from the hot working gas requires a radiator, which increases the complexity and cost of the engine while reducing its efficiency. The cost of electric power produced by a solar activated stilling engine is comparable to that of photovoltaic panels with the result that the subject invention has a substantial economic advantage.
The Ford Model T vehicle engine cooling method utilized a radiator to effect heat transfer from the coolant. The resultant temperature differences accomplished the required flow rate in the enclosed system between the cylinders to the radiator and return. The method did not include a coolant pump. The subject invention does not require a pump.
Gamoso, U.S. Pat. No. 5,870,892 teaches the conversion of potential energy of compressed air in a fluid through an air engine capturing this potential energy to drive a generator. Gamoso does not teach the use of a fluid flow driven by temperature gradients and its conversion of kinetic energy through a venturi flow system which drives an electrical generator, as in the present invention.
Solar thermal electric power is generated from the heat of the sun in systems using lenses and reflectors to concentrate the heat energy of the sun. In one method multiple solar parabolic troughs focus the sun""s energy on oil or molten salt circulating through pipes which are routed to a heat exchanger where steam is produced which drives a conventional turbine electric generator. In another configuration, a tower is at the center of a surrounding array of heliostat mirrors which track the sun reflecting the solar radiation to a receiver in the focal point center of the tower. Th e collected heat energy is used to create steam, which drives a conventional turbine electric generator. The operating temperatures and scale of these systems is substantial as is their generation capacity, normally in the hundreds of megawatts. As a result these systems do not offer power generation on a distributed basis but must rely on the grid to distribute their power generation. These systems in present practice do not provide the distributed, low cost service offered by the subject invention.
Prior art related to photochromic compounds includes two patents of the inventor;
Sangster, et al. U.S. Pat. No. 6,123,868 (September 2000) teaches the use of a photochromic compound attached to a biopolymer, as a medium to capture and release heat. In this patent Sangster does not teach implementation of the compound in a heat transfer means to create density differences or a venturi to create increased flow rate of the compound increasing kinetic energy which is converted to electricity as in the present invention.
Sangster, et al. U.S. Pat. No. 5,626,020 (May 1997) teaches the use of a photochromic heat exchange medium applied in a cooling and air conditioning system to store and release heat. This patent does not teach the use of these compounds as a means to increase flow and effect an energy conversion from kinetic energy to electricity as in the present invention.
There is a substantial body of prior art on photochromic compounds and their extensive use in optical devices to modulate light transmission. These applications do not implement heat containment and are therefore not comparable to the present invention.
There is also a vast body of prior art, which describes the difference in density of fluids and their flow through venturi systems, used in instruments or flow meters to detect the amount of energy in that flow.
U.S. Pat. No. 6,123,868 September 2000 Sangster et al.
U.S. Pat. No. 5,870,892 February 1999 Gamoso
U.S. Pat. No. 5,626,020 May 1997 Sangster et al
U.S. Pat. No. 5,513,494 May 1996 Flynn et al
1. xe2x80x9cAn Energy Conversion Method by Using Density Difference of Waterxe2x80x9d, Hitoshi Mochizuki, in Electrical Engineering in Japan, Vol 118, No 2, 1997.
We believe that the referenced prior art does not teach the present invention.
Several objects and advantages of the invention are,
The exposure of a photochromic heat exchange medium to solar heat in a panel. Occluded dark tubing in the initial section of the panel absorbs and transfers the heat of the sun to the flowing medium. On contact with heat the molecular structure of the medium closes effecting the storage of heat. Implementation of the reversion of the molecular structure of the medium to an open state releasing heat contained in the medium is accomplished in the following section of the panel by continued flow through clear tubing exposing the medium to sunlight. The medium then flows to the generator section. Flow of the medium is in a closed system.
Alternatively, the heated medium retaining heat in its closed molecular state is conveyed to a storage container. When release of heat is required the medium is conveyed through clear tubing where on exposure to artificial strobe light the molecular structure opens, releasing heat.
Acceleration of the flow rate of the medium is accomplished by a density differential between the heat bearing medium and the temperature of the conveying tubing and venturi due to the exterior of the those structures being surrounded by a cooler bath contained within the enclosure of the generator
Configuration of the latter section of the generator as a venturi further accelerates the flow rate of the medium.
The energy of flow of the medium is squared on conversion to kinetic energy where, in the last section of the venturi, that energy drives an impeller attached to the stator of a generator, which generates electricity.
Absorption and transfer of the heat transferred from the medium to the bath surrounding the generation section is accomplished by an enclosed impervious heat exchanger. The heat exchanger located inside and at the top of the generator enclosure absorbs heat in circulating potable water, which supplies heated water for use within the structure served by the generator. Thereby reducing the energy required to heat water.